1. Technical Field
This invention relates generally to seal assemblies, and more particularly to non-contact seal assemblies for roller bearings.
2. Related Art
It is known to provide seals for sealed, self-contained bearing assemblies with preset clearances and lubrication. Being preset and lubricated, these bearings can be fitted over an axle journal and within a housing to enable relative rotation between the axle and the housing. These bearings have experienced wide-spread use on axles of railway cars, but they are also used in other applications, such as for crane wheels, table rolls and shears, and even for the work rolls of rolling mills, for example. When used in railway car applications, the bearings are subjected to high levels of contaminants, such as moisture, dirt and debris. In order to maintain the useful life of the bearing, the contaminants must remain external to the oil side of the bearing. Accordingly, the seals in these bearings play a vital role in prolonging the useful life of the bearings.
Seals for railway bearings are known to have an outer case configured for attachment to an outer race of the bearing and an elastomeric seal element bonded to the seal case. The seal element typically extends radially inwardly from the outer case adjacent an oil side of the bearing to a primary lip that bears against an axially extending surface of a wear ring located adjacent to the inner race of the bearing. The seal element sometimes include secondary lips configured axially outwardly adjacent an air side of the bearing to bear against a radially extending leg of the wear ring. To maintain sealing engagement between the primary lip and the wear ring, a garter spring is commonly used to encircle the primary lip to force it snugly against the wear ring. The secondary lip is typically maintained in contact with the wear ring under the bias of the elastomer material from which the seal element is constructed. With the primary lip being biased into engagement with the wear ring, the primary lip generally provides such an effective barrier to the egress of the lubricant from within the bearing along the wear ring, that it is known for the secondary lip to starve for lubrication and to overheat. This, can cause the secondary lip to harden, thereby diminishing the overall effectiveness of the seal. In addition, the friction generated by the primary and secondary seal lips against the wear ring impart a measure of resistance to rotation, which tends to cause undue wear to the seal, and further, requires additional energy to overcome, thereby diminishing the efficiencies of the engine powering the railcar.
The seal of the present invention, among other things, including economic benefits realized from constructing various embodiments discussed herein, operates with considerably less torque than conventional seals of the type currently utilized with the bearings discussed above. Moreover, it provides a generally continuous width labyrinth passage from an air side of the seal to an oil side of the seal to prevent the ingress of contaminants.